A technique to join a resin member and a metal member is required in a wide range of fields such as the manufacturing of components used in, for example, an automobile, a home appliance, an industrial device, and the like.
In recent years, as the technique to join a resin member and a metal member, a method of joining a resin member and a metal member by injection molding the resin member into the metal member, that is, a so-called ‘injection joining method’ has been proposed.
In the injection joining method, for example, a resin member and a metal member are joined together by injecting into the metal member having fine protrusions and recesses on the surface an engineering plastic having a polar group with an affinity to the metal member. Narutomi and colleagues along with Taisei plas Co., Ltd. have been conducting active studies regarding the injection joining method, and the technique is described in patent documents (for example, Patent Documents 1 to 5 and the like).
Narutomi and colleagues disclose a technique to join by injection a polybutylene terephthalate resin (hereinafter, referred to as ‘PBT’) or a polyphenylene sulfide resin (hereinafter, referred to as ‘PPS’) to an aluminum alloy (for example, refer to Patent Document 1). In addition, a technique in which a large hole is provided in an anode oxide film of an aluminum material, and a synthetic resin body is fused into the hole, and is fixed using an anchor effect is disclosed (for example, refer to Patent Document 2).
A non-polar polyolefin having no affinity to a metal member is not easily attachable to a metal member. On the other hand, an acid-modified body of a polyolefin into which a polar group has been introduced can be attached to a metal member. However, for the attachment, it is necessary to hold the polyolefin in a melted state, and maintain the metal member and the polyolefin in contact with each other at a high pressure for a long period of time. Therefore, generally, a polyolefin and a metal member are joined together using a lamination method through melt extrusion, a pressing method, or the like.